A passive optical network (PON) is a point-to-multipoint, fiber-to-premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises, typically 16-128 premises. A PON may comprise an optical line terminal (OLT) at the service provider's central office and a number of optical network terminals (ONTs) near end users. A PON reduces the amount of fiber and central office equipment required compared with point-to-point architectures. A passive optical network is a form of fiber-optic access network.
In legacy TDM PON systems, downstream signals are broadcasted to all premises sharing multiple fibers. Upstream signals are combined using a multiple access protocol, usually time division multiple access (TDMA). The OLTs may “range” the ONTs in order to provide time slot assignments for upstream communication.
A PON takes advantage of wavelength division multiplexing (WDM), using one wavelength for downstream traffic and another for upstream traffic on a single non-zero dispersion-shifted fiber. Several protocols are implemented with the same basic wavelength plan and use the 1,490 nanometer (nm) wavelength for downstream traffic and 1310 nm wavelength for upstream traffic. 1550 nm is reserved for optional overlay services, typically RF (analog) video. There are heretofore unaddressed needs with previous optical networking solutions.